As pointed on CVE-2011-1146, some API forgot to check the read-only
status of the connection for entry point which modify the state
of the system or may lead to a remote execution using user data.
The entry points concerned are:
- virConnectDomainXMLToNative
- virNodeDeviceDettach
- virNodeDeviceReAttach
- virNodeDeviceReset
- virDomainRevertToSnapshot
- virDomainSnapshotDelete

* src/libvirt.c: fix the above set of entry points to error on read-only
connections